1. Field of the Invention
The present invention relates to a magnetic head for perpendicular magnetic recording that is used for writing data on a recording medium by means of a perpendicular magnetic recording system, and to a method of manufacturing such a magnetic head.
2. Description of the Related Art
The recording systems of magnetic read/write apparatuses include a longitudinal magnetic recording system wherein signals are magnetized in a direction along the plane of the recording medium (the longitudinal direction) and a perpendicular magnetic recording system wherein signals are magnetized in a direction perpendicular to the plane of the recording medium. It is known that the perpendicular magnetic recording system is harder to be affected by thermal fluctuation of the recording medium and capable of providing higher linear recording density, compared with the longitudinal magnetic recording system.
Typically, magnetic heads for perpendicular magnetic recording have a structure in which a read head having a magnetoresistive element (hereinafter, also referred to an MR element) for reading and a write head having an induction-type electromagnetic transducer for writing are stacked on a substrate, as is the case with magnetic heads for longitudinal magnetic recording. The write head includes a pole layer that produces a magnetic field in the direction perpendicular to the plane of the recording medium. The pole layer includes, for example, a track width defining portion having an end located in a medium facing surface that faces toward the recording medium, and a wide portion that is coupled to the other end of the track width defining portion and that is greater in width than the track width defining portion. The track width defining portion has a nearly uniform width. To achieve a higher recording density, a reduction in track width and an improvement in write characteristics, such as an overwrite property that is a parameter indicating an overwriting capability, are required of a write head of the perpendicular magnetic recording system.
As a magnetic head for perpendicular magnetic recording, there is known a magnetic head including a shield, the shield having an end face located in the medium facing surface at a position forward of the end face of the pole layer along the direction of travel of the recording medium with a predetermined distance provided therebetween, as disclosed in U.S. Patent Application Publication No. 2005/0219747 A1, for example. A gap layer made of a nonmagnetic material is provided between the pole layer and the shield. The shield has a function of preventing a magnetic flux from reaching the recording medium, the flux being generated from the end face of the pole layer and expanding in directions except the direction perpendicular to the plane of the recording medium. A magnetic head including such a shield enables a further improvement in recording density.
A magnetic head for use in a magnetic disk drive such as a hard disk drive is typically provided in a slider. The slider has the medium facing surface mentioned above. The medium facing surface has an air-inflow-side end and an air-outflow-side end. The slider is designed to slightly fly over the surface of the recording medium by means of an airflow that comes from the air-inflow-side end into the space between the medium facing surface and the recording medium. The magnetic head is typically disposed near the air-outflow-side end of the medium facing surface of the slider. In a magnetic disk drive, the magnetic head is aligned through the use of a rotary actuator, for example. In this case, the magnetic head moves over the recording medium along a circular orbit centered on the center of rotation of the rotary actuator. In such, a magnetic disk drive, a tilt of the magnetic head with respect to the tangent of the circular track, which is called a skew, occurs in accordance with the position of the magnetic head across the tracks.
In a magnetic disk drive of the perpendicular magnetic recording system, in particular, which exhibits a better capability of writing on a recording medium compared with the longitudinal magnetic recording system, the skew mentioned above often causes a phenomenon in which, when data is written on a certain track, data stored on a track adjacent thereto is erased (this phenomenon is hereinafter called adjacent track erasing). To achieve a higher recording density, it is required to suppress the adjacent track erasing.
As a technique for preventing the adjacent track erasing resulting from the skew mentioned above, it is effective to form a tapered surface in the top surface of the pole layer near the medium facing surface such that the thickness of the pole layer near the medium facing surface decreases with decreasing distance from the medium facing surface, as disclosed in U.S. Patent Application Publication No. 2005/0219747 A1. This technique allows a reduction in thickness of the track width defining portion in the medium facing surface, thereby making it possible to suppress the adjacent track erasing resulting from the skew. This technique also allows guiding a magnetic flux of great magnitude to the medium facing surface through the pole layer, thereby making it possible to suppress degradation of the write characteristics (overwrite property).
As a technique for preventing the adjacent track erasing in a write head of the perpendicular magnetic recording system, providing a side shield layer as disclosed in U.S. Patent Application Publication No. 2007/0177301 A1 is also effective.
In a magnetic head for perpendicular magnetic recording, flux leakage from the pole layer to the outside is likely to occur in a location near the boundary between the track width defining portion and the wide portion of the pole layer where the width of the pole layer abruptly changes. When providing a side shield layer in such a magnetic head, the side shield layer is to be disposed near the boundary between the track width defining portion and the wide portion where flux leakage is likely to occur. This can result in a problem that a magnetic flux leaks from the pole layer to the side shield layer to cause degradation of the write characteristics (overwrite property).